1. Field of the Invention
A method utilized in a wireless communication and related communication device are disclosed, and more particularly, to a method for random access channel optimization in a wireless communication system and related communication device.
2. Description of the Prior Art
A long-term evolution (LTE) system, initiated by the third generation partnership project (3GPP), is now being regarded as a new radio interface and radio network architecture that provides a high data rate, low latency, packet optimization, and improved system capacity and coverage. In the LTE system, an evolved universal terrestrial radio access network (E-UTRAN) includes a plurality of evolved Node-Bs (eNBs) and communicates with a plurality of mobile stations, also referred as user equipments (UEs).
In LTE system, random access channel (RACH) is an uplink channel, and is used to transfer control information from a UE to the network, e.g. for initial access to set up a connection or for location area updates. It can also be used for the transport of user data packets. Since the RACH channel is a contention based channel where several users might access the same resource, the RACH configuration has critical impacts to system performance. For example, the RACH collision probability is significantly affected by the RACH configuration, thereby making this a critical factor for call setup delays, data resuming delays from the uplink unsynchronized state, and handover delays. In addition, the RACH configuration also affects the call setup success rate and handover success rate.
In order to improve the system performance, RACH optimization functionality is introduced in the LTE system. The network may perform the RACH optimization for optimizing the RACH configuration, thereby increasing efficiency as well as improving the system performance. In addition, a random access procedure is performed for collecting RACH parameters. The UE stores the collected RACH parameters after the random access procedure, and waits for the network to request for the collected RACH results for RACH optimization. Therefore, the network can perform the RACH optimization according to the collected RACH results.
However, how the network requests for the collected RACH results is not clearly specified, thereby affecting process of the RACH optimization. That is, how the UE reports the RACH results is never concerned. Moreover, the UE may not maintain the RACH results. Thus, when the network requests the UE to send the RACH results, the UE does not know how to deal with this situation. In other words, how the network shall handle the situation that the network requests for the RACH results but the UE does not have any of the RACH results is not clearly defined.